The present invention relates to a check fixture for a spherical bearing, and more particularly to a hand-held check fixture for a spherical bearing in a helicopter pitch change link.
Helicopter rotor assemblies typically include a series of pitch change links (sometimes referred to as pitch links) for controlling the pitch of the rotor blades. The pitch change links can extend between an upper swashplate and a rotor blade hub. During use, a pitch change link generally supports compressive loads and tensile loads exerted by the upper swashplate. As the position and attitude of the upper swashplate varies, the pitch of each rotor blade also varies. In fully articulating rotor assemblies, the pitch of each rotor blade varies rapidly to generate both aerodynamic lift and aerodynamic thrust.
Pitch change links are typically threaded at one end and include a ball joint at the other end. The ball joint can include a ball bearing seated within a knuckle. The ball bearing is generally seated securely within the knuckle with a limited clearance between the ball bearing and the knuckle. Over the normal use of a pitch change link, the ball joint can develop an excessive clearance between the ball bearing and the knuckle, causing the ball bearing to repeatedly impact the knuckle during flight. As a result, the pitch change link can wear outside of acceptable limits, in many instances made worse by the exposure of the ball joint to moisture and blowing sand or dust. This wear can affect overall helicopter flight handling characteristics, and can cause erratic or unpredictable behavior of the airframe during flight operations.
As a result, the pitch change link is normally subject to periodic inspection. A typical inspection can include removing the pitch change link from the rotor assembly, examining the ball joint for excessive play, and reinstalling the pitch change link. According to current methods for inspection, the pitch change link is normally removed and reinstalled at both ends, that is, at the ball joint and at the threaded end portion. In addition, the removal of the pitch change link from the helicopter can in many instances require added evaluations and/or recertifications before the helicopter can return to flight operations.
While periodic inspection of the pitch change link can be an effective method of detecting excessive play between the ball and the knuckle, current methods of inspection are time consuming and involve the disassembly and removal of the entire pitch change link from the rotor assembly. Accordingly, there remains a need for an improved system for inspecting pitch change links. In particular, there remains a need for an improved system to quickly and effectively detect excessive play in a pitch change link ball joint.